I am using a revenue night and the rest points for the additional nights
The 15k standard award is unavailable so only Regency Clubs rooms are available at the 18 per night redemption.
IMO the Mission Bay property is worth its normal 15k a night asking redemption cost but not 18k a night for a Regency Club room as a Diamond member.So its a premium per night where I receive nothing in return.

When one remains loyal to a program for many years and continues to receive value year round at most properties it allows me to justify the use of revenue and higher awards when I haven't planned enough in advance during a high demand time.It’s about the relationship overall. In addition and somewhat off topic I am also trying to close in on lifetime Diamond as difficult as it is to achieve based on Gold Passports policy of points only stays excluding any eligible spending when earning miles for a stay.